There’s no better time to wax poetic about the importance of sun protection than in the summer. And while many of us have our go-to sunscreens and sun-fighting skin care products stocked year-round, the summer months might call for an added layer of protection—which is where UPF clothing comes in.

Not familiar with UPF? It's a rating system that stands for ultraviolet protection factor, and it measures the effectiveness of sun-protective fabrics in clothing. SPF used to be the catchall word for both skin care products and clothing that provide sun protection, but UPF is the new terminology for sun-protective clothing, specifically.

Luckily, for anyone who loves the great outdoors but hates sunburns, more and more activewear brands have been using the system to make clothing that will help you beat the summer's powerful rays. Brands like Noli Yoga, Boody Eco Wear, and Athleta offer a considerable selection of UPF athleisure options.

To be clear, most clothing fabrics can naturally block out ultraviolet radiation from the sun, explains Alan McLennan, a senior technical officer for UPF testing at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). The UPF label really just helps you understand how much. Similar to SPF, UPF protective numbers range from 15 to 50+. In the case that a particular fabric doesn't block out the sun, brands can use chemical additives to boost fabric’s UV-blocking properties.

When it comes to choosing UPF clothing, it's important to remember that sweat and water are two factors that can affect a fabric’s UPF abilities. "Even with a high UPF, repeated washing and exposure to sweat or water can lead to a decrease in UPF levels," says Cybele Fishman, M.D., an NYC-based dermatologist. She recommends sticking to a UPF of 50+ and retiring the piece once it's considerably stretched out since loose-fitting clothes can also decrease UPF.

And while UPF clothing can be just as effective as SPF products, Fishman suggests using the two together when outdoors for ultimate broad-spectrum protection. "If you’re going to be in the water a long time or out in the sun for a prolonged period of time, the safest thing is to wear sunscreen underneath UPF clothing." (And remember: Opt for natural, mineral-only sunscreens whenever possible.)

If you’re in the market to scoop up some UPF-approved pieces, keep in mind that factors like color and materials are important, Fishman says. "The darker the color and tighter weave of the fabric, the higher the UPF," she says. "Synthetics are better than cotton in terms of UMF, as they reflect more radiation rather than absorb it. Cotton is a UV absorber so not a good choice for sun-protective clothing.”

Whether you plan on continuing to use your trusty SPF or are interested in checking out your favorite athleisure brand's UPF offerings—or both—the important thing is that you protect yourself at all. So find a sun-protection routine that works for you, and stick to it.